The biological decontamination of soils polluted with metals, metalloids, industrial and agricultural organic waste and discharges or radio-isotopes as well as the treatment of effluents contaminated with metallic residues are problems of great concern as the soil performs essential functions which largely determine the production of food products and water quality.
Among the different polluting substances, heavy metals are among the most harmful compounds, as they are not biodegradable and become concentrated in the soils. Examples of sites exist in France, Belgium, Luxembourg, in the Jura, the Lower Swiss Alps or in the Pyrenees, to mention only the nearest regions as well as in more distant regions such as New Caledonia where nickel is more particularly exploited. Various African countries such as Gabon, Mali, South Africa, and also Mexico, China, India or Australia are also good examples.
Technologies for decontaminating soil are difficult to develop, as it is a heterogeneous, complex and dynamic medium, which plays a key role as a buffer and pollutant processor.
Different techniques of phytoremediation (phytoextraction, phytodegradation, phytostabilization, phytostimulation, phytotransformation, phytovolatilization and rhizofiltration) are currently being developed (Terry, N. and Banuelos G., editors, Phytoremediation of contaminated soil in water, Lewis Publishers, Boca Raton, Fla. 2000).
The CNRS is studying the technique of phytostabilization which consists of cultivating the contaminated soils with plants capable of growing in the presence of heavy metals (the term tolerance is used) (Frerot et al., Specific interactions between local metallicolous plants improve the phytostabilization of mine soils, Plant and Soil, 282, 53-65, 2006). Certain of these plant species used have the distinctive feature of accumulating large quantities of metals in their vacuoles (the term hyperaccumulating plants is used). Then it is a question of phytoextraction.
The team has quite particularly studied two plants; one of them, Thlaspi caerulescens (synonym Noccaea caerulescens) belonging to the Brassicaceae family, has remarkable properties of tolerance and hyperaccumulation of zinc, cadmium, nickel. It concentrates them in the aerial parts (leaves and stems).
This plant is capable of storing zinc at concentrations 100 times greater than that of a conventional plant. Moreover, it is capable of extracting and concentrating zinc and cadmium in the aerial tissues, even on soils having a low concentration of these two metals.
In addition to their unusual tolerance to Zn2+ and Cd2+ and to other metals, the hyperaccumulating plants are capable of extracting the metals and transferring them to the aerial parts where they are concentrated. Due to this fact, the roots have a very low heavy metal content, unlike non-accumulating plant species. This triple property of tolerance/accumulation/concentration in the parts which can be harvested is in fact a relevant tool in phytoremediation.
Moreover, heavy metals are commonly used in organic chemistry as catalysts that are indispensable to carrying out chemical conversions which require significant activation energy. The role of the catalysts is then to lower the energy barrier.
Their operating mode is frequently based on their Lewis acid properties. Zinc chloride is one of the most used and is indispensable in numerous industrial and laboratory reactions. It is also frequently used in heterocyclic organic chemistry for catalyzing numerous aromatic electrophilic substitutions.
It is also a catalyst of choice for carrying out hydrogenations of primary alcohols with Lucas' reagent, acetalization, aldolization reactions or cycloaddition reactions of the Diels-Alder type etc.
The catalysts are also very useful in analytical electrochemistry, electrometallurgy and liquid-solid extraction where the fields of application are numerous and directly involved in the different fields of economic life (batteries, fuel cells and accumulators, detectors of spectroscopic equipment, metallurgy, welding etc.)
In international application WO 2011/064462 and application WO 2011/064487 published on 3 Jun. 2011 the invention of Professor Grison and Doctor Escarré is described and claimed, which relates to the use of a calcined plant or a part of a calcined plant having accumulated at least one metal in the M(II) form chosen in particular from zinc (Zn), nickel (Ni) or copper (Cu), for the preparation of a composition containing at least one metal catalyst, the metal of which is one of the aforementioned metals in the M(II) form originating from said plant, said composition being devoid of chlorophyll, and allowing the implementation of organic synthesis reactions involving said catalyst.
In addition to the species mentioned above, Thlaspi caerulescens which is now called Noccaea caerulescens and Anthyllis vulneraria, application WO 2011/064487 describes the use of numerous other metallophyte plants which are hyperaccumulators of heavy metals for the preparation of catalysts which can be used in organic chemistry.
Therefore the invention described in WO 2011/064487 relates to the use of a calcined plant or part of a calcined plant having accumulated at least one metal in the M(II) form chosen in particular from zinc (Zn), nickel (Ni) or copper (Cu) as defined above, in which said plant is chosen in particular from the Brassicaceae family, in particular the species of the genus Thlaspi (synonym Noccaea) in particular T. goesingense, T. tatrense, T. rotundifolium, T. praecox, the species of the genus Arabidopsis, in particular Arabidopsis hallerii, and the genus Alyssum, in particular A. bertolonii, A. serpyllifolium, the Fabaceae, the Sapotaceae, in particular the species Sebertia acuminata, Planchonella oxyedra, the Convolvulaceae, in particular the species Ipomea alpina, the Rubiaceae, in particular the species Psychotria douarrei, in particular P. costivenia, P. clementis, P. vanhermanii, the Cunoniaceae, in particular the Geissois, the Scrophulariaceae, in particular the species of the genus Bacopa, in particular Bacopa monnieri, algae, in particular red algae, in particular the rhodophytes, more particularly Rhodophyta bostrychia, green algae or brown algae.
Due to this fact, the plant waste is directly recovered and converted to “green” catalysts or to unconventional reagents.
In French patent application No. 12/52045 filed on 6 Mar. 2012 and not yet published, Professor Grison and researchers Escande and Losfeld have unexpectedly shown that certain other plants which belong to the genus Sedum as well as a different plant, Potentilla griffithii, have metallophyte properties for hyperaccumulating different heavy metals which make them particularly interesting for use in organic chemistry catalysis.
The plants of the genus Sedum are succulents which belong to the Crassulaceae family, composed of more of 400 species. They have the natural aptitude to grow on poor, dry soils, in an open environment and under difficult conditions. Their foliar system is fleshy and they are easy to cultivate.
Among them, three species have developed unusual properties of extracting zinc and cadmium. Sedum plumbizincicola and Sedum jinianum have in particular a remarkable ability to extract zinc from the polluted soils of the south and east of China. They have real potential for phytoextraction and are described as “plumbizincicolafor”.
However, the application of extracts of these plants as catalysts has never been described before and is the subject of French patent application No. 12/52045.
Professor Grison's team then discovered that the richness of the soil in mineral species such as manganese, can also be the basis for the progressive adaptation of plant communities, which become tolerant and hyperaccumulators of metallic trace elements, in particular Mn (II).
The following are examples of genera of plants comprising manganese hyperaccumulating species:
Alyxia, Azolla, Beauprea, Beaupreopsis, Bridelia, Crotalaria, Dicranopteris, Dipteris, Eugenia, Garciania, Gleichenia, Gossia, Grevillea, Macadamia, Maytenus, Pinus, Spermacone, Stenocarpus, Virotia. 
These metallophyte species are thus capable of concentrating up to 110,000 ppm of manganese (as dry matter) in their foliar system. Their ability to grow on eroded mining sites, depleted of organic matter and exposed to dryness, makes these plants very useful for the ecological restoration of sites severely damaged by intensive mining operations.
The cultivation of such species, such as for example those of the genus Grevillea, has a use in addition to ecological restoration. They are the basis of new Lewis acid catalysts and high performance oxidizing reagents, the reactivity of which can be adjusted by controlling the degree of oxidation of the Mn and the composition of the medium. In the context of environmental crisis and tightening of European chemical regulations, the development of new mild, effective oxidizing systems which are environmentally sustainable is a real opportunity.
The treatments and preparations of the catalysts and oxidizing systems are easy, straightforward to implement and comply with green and ecological constraints.
The use of these plants is described and claimed in French application FR 12/57135, not yet published.
In European patent application No. EP 13 305 208, also not yet published, Professor Grison's team then discovered that certain plants chosen from Psychotria douarrei, Geissois Pruinosa, Alyssum murale, Noccaea caerulescens and Anthyllis vulneraria had the property of accumulating large quantities of Nickel (Ni) and could be used in preparing catalysts which can be used in organic chemistry.
Moreover, the chemistry of the platinoids represents a field essential for organic synthesis, that of reactions catalyzed by precious metals: platinum, palladium, osmium, iridium, ruthenium and rhodium. This field of chemistry is indispensable to the fine chemicals sectors: pharmacy, agri-food, agrochemistry, cosmetics and perfumery.
However, access to resources has become a key problem: they are mainly concentrated in a limited number of countries which are often politically unstable; worldwide resources worldwides are becoming depleted; ore extraction is contributing to the increase in energy costs. This general context is leading to a record increase in the cost of production.
Faced with such a situation, innovative recycling methods give the platinoids considerable significance.
The inventors of the applications mentioned above have shown that growing plants that accumulate metal cations on degraded mining sites, or in polluted aqueous environments, then recovering them for catalytic chemistry made it possible to resolve two major difficulties:                the bio-sourced catalysts make it possible to develop, heterogeneous catalysts that are very useful because they can be recovered by simple filtration and rinsing; they are therefore recyclable.        their performances are analogous to or better than those of their soluble homologues.        
These results represent a true revolution in the field of catalytic chemistry. They also constitute a very attractive solution for overcoming the ecological and environmental problems of post-mining activities or treatment of industrial effluents.